强磁场诱导下LSO:Ce闪烁陶瓷的晶粒定向排布及光学透明性优化

Low-symmetry ceramics are the important development direction of scintillation materials, but the low transparency resulting from anisotropic structure become an urgent problem need to solve. Therefore, how to effectively design the microstructure and enhance the transparency of the low-symmetry ceramics was the breakthrough. Cerium-doped lutetium oxyorthosilicate (Lu2SiO5:Ce, LSO:Ce), a monoclinic material with excellent properties of high density, high light yield and fast decay time was selected in this project based on our previous work. Through calculation of electronic structure, magnetic and optical parameters, the magnetic properties and optical properties of LSO:Ce will be predicted and its potential of grain orientation will be evaluated. Through analysis of thermodynamics and kinetics, the mechanism of grain orientation in the strong magnetic field will be investigated systematically from four aspects of materials composition, slip casting, densification and microstructure. The highly transparent LSO:Ce ceramics and its fabrication technology will be achievedA new calculation method will be developed through the correlation investigation of structure-property-calculation parameters. Theoretical basis and research methods to design and develop more optical ceramics with low-symmetry structure will be achieved.

低对称晶系陶瓷是未来闪烁材料的重要发展方向，但其各向异性晶体结构特点导致其光学透明性偏低，成为这一类材料亟待解决的问题。因而如何有效地设计这类陶瓷的显微结构和提高其光学透明性成为突破口。本项目拟在前期工作基础上，选择具有高密度、高光产额、短衰减时间等优良特性的单斜晶系铈掺杂硅酸镥(Lu2SiO5:Ce，简写为LSO:Ce)为研究对象，通过对电子结构、磁学参量、光学参量的计算，预测该材料的磁学和光学性能及其晶粒定向排布潜能。通过热力学和动力学分析，从LSO:Ce的材料组分、成型过程、致密化过程和显微结构方面系统研究低对称晶系陶瓷晶粒在强磁场下的排布机理，获取高光学透明性LSO:Ce陶瓷材料及其制备技术。通过研究结构、性能、计算参量间的相互关系，发展新的计算方法，为低对称晶系光学陶瓷材料的设计和开发提供理论基础和研究方法。

为提高低对称晶系陶瓷材料的透明性，以单斜晶系LSO:Ce为研究对象。采用第一性原理计算，研究了LSO:Ce材料的光学各向异性，其折射率最大差值为0.021；采用PPMS研究了LSO:Ce单晶的磁各向异性, 其磁化率最大差值为7.7×10-8。通过溶胶-凝胶合成工艺在1200℃合成了单相LSO:Ce粉体。研究湿法球磨工艺、分散剂种类和含量，LSO:Ce料浆的分散性和粘度影响规律。研究了粉体晶粒尺寸、料浆粘度、化学组成对于LSO:Ce陶瓷织构度的影响规律。在固含量为35vol.%的料浆中添加0.2wt.%聚丙烯酸胺（NHPA），并通过24h的球磨获得了粘度为70mPa⋅s (剪切速率为4s-1)高分散性LSO:Ce料浆。系统研究了晶粒尺寸、料浆粘度和磁场强度对LSO:Ce陶瓷织构度的影响规律。在9T强磁场下通过注浆成型和后续1650℃的无压烧结及热等静压烧结获得了织构度为0.48，相对密度为98.8%的织构化LSO:Ce陶瓷。通过少量的Gd引入，在6T强磁场下注浆成型和后续1650℃的无压烧结得到了晶粒取向度为96%的织构化LGSO:Ce陶瓷。通过XRD数据和粘度数据，提出了LSO:Ce晶粒在强磁场中的a, c双轴旋转规律。